Investigators will look for evidence that Google lowered the results position of rival services such as price comparison sites in its unpaid results. The commission will also look at allegations that Google unfairly lowered the "Quality Score" for sponsored links of competing services.

The European Commission also plans to investigate claims that Google imposes exclusivity agreements with advertisers which prevent them from displaying adverts from rival search services on their own sites.

It will also look at allegations of restrictions of the portability of online advertising campaign data to other online advertising platforms.

The Commission said that the opening of an investigation in no way suggested the search giant was guilty of anti-trust offences.

Google sent us the following: “Since we started Google, we have worked hard to do the right thing by our users and our industry – ensuring that ads are always clearly marked, making it easy for users to take their data with them when they switch services and investing heavily in open source projects. But there’s always going to be room for improvement, and so we’ll be working with the commission to address any concerns.”